The process of European integration has created a multilevel federal polity in which regionalist parties can thrive. The European Union (EU) significantly reduced the cost of autonomy and...Show moreThe process of European integration has created a multilevel federal polity in which regionalist parties can thrive. The European Union (EU) significantly reduced the cost of autonomy and independence for regions, as it provides a viable alternative to belonging to a central state. Consequently, regionalist parties are more viable in the eyes of the electorate. Moreover, the EU has created a space that Member States cannot fully control. These two factors have thus contributed to the rise of regionalist parties in Europe. However, this cannot account for the discrepancies in electoral success between regionalist parties across Europe. This thesis seeks to account for these discrepancies by analysing the relative importance of domestic factors on the rise of regionalist parties. In that pursuit, this thesis compares Catalonia and Friesland. In Catalonia, domestic factors provided the momentum for the rise of regionalist parties, but European integration made them viable. In Friesland, the opposite holds true. Domestic variables and, in part, European integration itself, inhibited the rise of the Frisian Nationalist Party. European integration is therefore only relevant in relation to domestic factors and vice versa. As such, only an integrated approach can adequately account for the rise of regionalist parties in Europe.Show less